Di-ester fluids with improved water tolerance



DI-ESTER FLUIDS WITH rinnovan WATER TOLERANCE Theodore W. Langer,Buffalo, and Blake F. Mago, North Tonawanda, N.Y., assignors to UnionCarbide Corporation, a corporation of New York No Drawing. Filed Nov.14, 1955, Ser. No. 546,790

9 Claims. (Cl. 252-475) This invention generally relates to aliphaticdi-ester fluids having improved water tolerance. It is concerned moreparticularly with mixtures of such di-esters with polyoxyalkyleneglycols.

Di-ester type fluids, including substituted adipates, azelates andsebacates, find extensive use as high temperature turbine lubricants foraircraft engines, instruments and in general wherever excellentviscosity-solubility and viscosity-temperature properties are needed.These fluids, however, possess the unwanted tendency of dissolving orabsorbing small amounts of Water. This solubility decreases at lowertemperatures, and condensate absorbed by the fluids at operatingtemperatures later precipitates as ice after shut down at wintertemperatures. Precipitation of the thus formed ice in oil lines or atnozzles can cause clogging.

It has been found that the water tolerance and viscometric stability ofthe above di-ester fluids can be increased by the addition ofpolyoxyalkylene glycol derivatives. These derivatives are the additionproducts formed by the reaction of an alcohol with ethylene oxide, orpropylene oxide or a mixture of these oxides in which the ratios of therespective oxides are from about 25 percent-75 percent to 75 percent-25percent. Such products are viscous liquids of relatively high averagemolecular weight, and actually are complex mixtures of polyoxyalkylenechains having different lengths. For a further and more detaileddescription of the additives of the invention, reference is made to US.Patents 2,425,755 and 2,425,845, issued August 19, 1947, in the namesrespectively of F. H. Roberts et a1. and W. J. Toussaint et al.

The lubricant fluid of the invention thus comprises a mixture ofdi-alkyl esters of simple and substituted d-i-basic acids having from 6to 10 carbon atoms, and polyoxy alkylene glycols and mono and di-etherderivatives thereof having a viscosity ranging from 59 to 3000 SUS at100 F.

' To illustrate the eifectiveness of the additives of the invention inimproving the water tolerance of di-esters, cloud point determinationswere made on two of these.

The cloud point is the temperature at which a definite turbidity isnoted on cooling the fluid. This was determined by observing the samplein a test tube immersed in a cold bath. A thermometer placed in thesample was read when turbidity was first evident.

Patented July 12, 1960 Table I indicates that as di-esters absorb waterfrom the atmosphere, their cloud points are raised objectionably. Aquantity of di-2-ethylhexyl sebacate as received from a manufacturercontained 0.06 percent water, and di-2-ethylhexyl adipate from anothersource absorbed 0.09 percent water; Accordingly, both were turbid onstanding at about 20 F.

Table 'II cites examples showing that the water tolerance ofdi-Z-ethylhexyl adipate was increased appreciably by the addition ofvarious polyoxyalkylene glycol derivatives.

A is a polyoxypropylene glycol monobutyl ether having a viscosity of3,000 SUS at F.

B is a polyoxypropylene glycol dibutyl ether having a viscosity of SUSat 100 F. C is a butyl ethyl diether of a polyalkylene glycol made froma 5050 mixture of propylene and ethylene oxide with the final dietherhaving a viscosity of 59 SUS at 100 F.

TABLE H Examples 1 to 8 Cloud Point with Dl-2- Polyalkylene EthylhexylAdipate, F. Example 1-8 Glycol Derivative 0.11% Water 0.16% Water -14+16 -30 +6 32 +6 -52 -30 30 +5 52 30 -70 45 Below -70 Other diestersshow similar beneficial effects from ad- Also, addition of 5 percentpolyglycol B to di-Z-ethyl- 'hexyl sebacate containing 0.06 percent ofwater by Karl Fischer analysis lowered the ester cloud point from 20 F.to below the pour point of the fluid. Storage. tests of 72 hoursduration at a 65 F. temperature with di-2- ethylhexyl ad-ipatecontaining 0.09 percent water indicated that 10 percent of polypropyleneoxide monobutyl ether of a viscosity of 525 Saybolt Universal seconds(SUS), 6.5 percent of the same type of polyglycol having a viscosity of1145 Saybolt seconds or 6 percent of the samehav-ing a viscosity of 1715Saybolt seconds, or 22.5 percent polypropoxy dibutyl ether of aviscosity of 130 Saybolt seconds, result in clear blends. This is to becontrasted with samples of the adipate alone or mixed withpolymethylmethacrylate thickeners which become turbid afiter similarexposure.

Another advantage of mixtures of di-esters with poly-' oxyalkyleneglycols is the marked improved-temperature TABLE IV Examples 12 to 18Corrosion-inhibited Blend Con- Viscosity (cstks) Hardi- Exaruple tamingTricresyl Phosphate man and and 0.5% Phenothiazine Nissan 210 F. 100 F.65 F. V.I.

12 Di-2ethy1hexyl sebacate 3.35 13.3 12,600 143 13 Di-2-ethylhexyladipate 2. 40 8.45 6,650 130 14 Dl-Z-ethylhexyl adipate plus 5 per- 3.14 11.27 154 cent of A. 15 Di-2-ethylhexyl adipate plus 22.5 3.01 11.1012, 400 149 percent of B. 16 Mixed alcohol pimelate 2. 33 7. 94 150 17Mixed alcohol pimelate plus 6 per- 3. 26 11. 36 7, 650 159 cent of A. 18Mixed alcohol pimelate plus 25 3.10 11.07 9, 450 154 percent of B. p

The foregoing additives in general gave better performance thanunblocked polyglycols such as polypropylene glycol. Such compounds haveapplicability in particular cases. Typically the performance ofpolypropylene glycol appears in Table V.

It is to be understood that the benefits obtained by the addition ofpolyoxyalkylene glycols to aliphatic di-ester fluids are realized in thepresence of other agents which may be added to the base fluids toovercome other performance problems. The end use of these fluids, forexample, hydraulic fluids for aircraft engines, may require theinclusion of other additives for control of oxidation, lubricity,corrosion and viscosity tailoring. Oxidation control additives generallyconsist of aromatic amines such as phenothiazine or substituted phenols,and sometimes may contain sulfur. Improved lubricity or load-carryingability can be secured by the addition of organophosphate compounds ofthe type obtained by the reaction of inorganic phosphorus compounds withpetroleum fractions (exampletricresylphosphate). Conventional corrosionproblems are resolved through the selection of base fluid blends,together with proper choosing of additives for other purposes, as Wellas by the addition of specific corrosion inhibitors. Viscosity tailoringof fluid may be eflccted by the addition of selected polymers such aspolymethylmethacryl-ate or silo-xanes. Accordingly, variousmodifications and variations may be effected as regards theseconventional additives without departing from therange of the inventionor from the scope of the appended claims.

What is claimed is:

1. A lubricant fluid having improved viscometric stability and lowtemperature Water tolerance consisting of 5 percent polyoxypropyleneglycol monobutyl ether, 5 percent tri-cresyl phosphate, 0.5 percentphenothiazine, the balance di-Z-ethylhexyl adipate, said mixture havinga Hardiman and Nissan viscosity index of 15-4.

2. A lubricant fluid consisting of a mixture of di-2- ethylhexyl adipateplus 22 /2 percent of polyoxyprop y-lene glycol dibutyl other, 5 percenttri-cresyl phosphate and 0.5 percent of phenothiazine, said mixturehaving a viscosity of about 12,000 centistokes at --6'5 F. and aH-ardiman and Nissan viscosity index of 149.

3. A lubricant fluid for gas turbine engines consisting of 6-percentpolyoxypropylene glycol monobutyl ether, 5 percent .tri-cresylphosphate, 10.5 percent phenothiazine, the balance consisting of mixedalcohol pimelates, said mixture having a viscosity of about 7,600centistokes at -65 F. and a Hardiman and Nissan viscosity index of about159.

4. A lubricant fluid for gas turbine engines consisting of 80 percentdi-Z-ethylhexyl adipa te and 20 percent of a polyoxypl'opylene glycoldibutyl ether having a viscosity of 130 Saybolt Universal seconds at 100F.

5. A lubricant fluid for gas turbine engines consisting of 90 percent ofdi-Z-ethylhexy-l adipate and 10 percent of a butyl ethyl diether of apolyoxya-lkylene glycol of a viscosity of 59 Saybolt Universal secondsat 100 F.

6. A lubricant and hydraulic fluid mixture having improved viscometricstability and low temperature water tolerance containing, in addiiion i0conventional additives for the control of oxidation, lubricity,corrosion and viscosity, 20 percent of polyoxypropylene glycol di-butylether having a viscosity of 130 Saybolt Universal seconds at 100 F thebalance being di-Z-ethylhexyl adipate.

7. A lubricant and hydraulic fluid mixture having improved viscometricstability and low temperature Water tolerance containing in addition toconventional additives for the control of oxidation, lubricity,corrosion and viscosity, 10 percent of a butyl ethyl di-ether of apolyoxyalkylene glycol having a viscosity of 59 Saybolt Universalseconds at 100" F., the balance being di-Z-ethylhexyl adipate.

8. A lubricant and hydraulic fluid having improved viscometric stabilityand low temperature water tolerance, consisting essentially of a mixturecomposed of at least one aliphatic diester selected from the groupconsisting of the higher alkyl adipates, sebacates, azelates andpimelatcs, and from 2 to 22% percent of at least one high viscosityalkyl polyoxyalkylene glycol other selected from the group consisting oflower alkyl monoand di-ethers of polyoxypropylene and polyoxyethylcneglycols, the vis cosity of said ether ranging from about 59 SayboltUniversal seconds to about 3000 Saybolt Universal seconds at F.

9. The fluid of claim 8 additionally characterized by the presencetherein of conventional additives for the control of oxidation,lubricity, corrosion and viscosity.

References Cited in the file of this patent OTHER REFERENCES Ucon,August 3, 1947, copyright 1947, by Carbide and Carbon Chem. Corp, NewYork, N.Y., pp. 6-9, 14 and 15.

8. A LUBRICANT AND HYDRAULIC FLUID HAVING IMPROVED VISCOMETRIC STABILITYAND LOW TEMPERATURE WATER TOLERANCE, CONSITING ESSENTIALLY OF A MIXTURECOMPOSED OF AT LEAST ONE ALIPHATIC DIESTER SELECTED FROM THE GROUPCONSISTING OF THE HIGHER ALKYL ADIPATES, SEBACATES, AZELATES ANDPIMELATES, AND FROM 2 TO 22 1/2 PERCENT OF AT LEAST ONE HIGH VISCOSITYALKYL POLYOXYALKYLENE GLYCOL ETHER SELECTED FROM THE GROUP CONSISTING OFLOWER ALKYL MONO- AND DI-ETHERS OF POLYOXYPROPYLENE AND POLYOXYETHYLENEGLYCOLS, THE VISCOSITY OF SAID ETHER RANGING FROM ABOUT 59 SAYBOLTUNIVERSALS SECONDS TO ABOUT 3000 SAYBOLT UNIVERSAL SECONDS AT 100*F.